Means to vapor deposit on a tubular substrate



Nov. 4, 1969 J. F. CLARKE 7 MEANS TO VAPOR DEPOSIT ON A TUBULAR SUBSTRATE Original Filed Oct. 13, 1965 FIG. I.

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United States Patent ABSTRACT OF THE DISCLOSURE Means to coat a freshly drawn tube wherein a hollow mandrel supports a plug element which cooperates with a die through which the tube is drawn. The hollow mandrel includes an outlet in front of the plug whereby gaseous coating stuff may be delivered into the tube in a direction of movement counter to the tube travel. A heating elementisdisposed so as to effect thermal decomposition of the delivered coating stuff. Additional means are provided whereby to coat the tubes external surface.

This is a division of application Serial No. 495,502, filed Oct. 13, 1965, now Patent No. 3,417,453.

Among the several objects of the invention may be noted the provision of a reliable means for making improved tubing having complete coating on its inside surface, and,'if desired, also on its outside surface; and the provision means to practice a low-cost continuous process which is particularly applicable to the manufacture of improved welded metal tubing having a continuous inside metal coating, and, if desired,'also a continuous outside metal coating. Other objects and features will be in part apparent and in part pointed out hereinafter.

Satisfactory commercial methods for continuously applying a metal coating to the inside of a metal tube have not been developed. Batch processes have been used; for example, by the extrusion of two coaxial tubes, followed by drawing to finished size. This, however, results in production in limited lengths and is expensive. An indirect continuous method exists, whereby a metal stripis first clad to a second metal strip, both then being bent into tubular form and seam-welded. This has the disadvantage that continuity of the inside facing of the tubing becomes impossible and can be approximated only by the use of very elaborate seaming techniques. By means of the present invention, a chemical vapor deposition of material is effected in a continuous process to overcome the abovementioned problems. i Y

The invention accordingly comprises the methods, constructions and products hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, illustrating one form of the invention,

FIG. 1 is a diagrammatic viewillustrating the process and apparatus for producing the tubing; and

FIG. 2 is an enlarged axial section of certain parts shown at the left of FIG. 1.

Referring now to the drawings, there is illustrated at numeral 1 a housing divided by a wall 3 into gas chambers 5 and 7. At numeral 9 is an inlet opening means into the chamber 5 for admitting a moving metal strip 11 from which desired metal tubing is to be formed. This opening means also admits a hollow mandrel or injection device 15 which carries a chemical vapor to be described.

Mounted on the wall 3 is a curling die 17 for receiving the moving strip 11 and converting it to the desired tubular form. This form may be circular, elliptical or the like, the circular form being illustrated. The curling die 17 is 3,476,080 Patented Nov. 4, 1969 shaped to bring together the two edges 19 of the strip as the tubular form leaves the die and moves through the chamber 7, as shown.

At numeral 21 is diagrammatically illustrated welding means for continuous fusion-welding of the edges 19 as the latter leave the die 17 to complete the desired tube, which is numbered 23. The station 20 for the welder 21 is near the outlet of die 17, as illustrated.

On a wall 25 of the chamber 7 is located a drawing or finishing die 27. This is related substantially coaxially with the curling die 17. The hollow mandrel 15 extends through the die 17 and spacedly withinthe tube 23 (see FIG. 2). At its end near the die 27 the mandrel 15 has a constriction 29 and an enclosing head 33. Openings 31 are provided through the constriction 29. The head 33 closes the end of the hollow mandrel 15 and substantially forms a dam in the tube 23 where his being finished in the die 27. At numeral 35 are shown draw rolls for pulling the tube 23 and the strip 11.

At numeral 37 is diagrammatically shown an electrical induction heating coil, located between the gas outlet openings 31 and the welding station 20. This coil 37 surrounds the tube 23 for providing a heating region or zone 38 for heating the tube in its welded condition as it advances from the welding station to the die 27.

At numeral 39 is shown an inlet for a suitable atmosphere of gas or vapor to be carried in the chamber 7. At numeral 41 is a valved outlet for controlling the flow of this atmosphere through the chamber 7. The nature of the gas to be employed in the chamber 7 will be discussed below:

At numeral 43 is a valved outlet from the chamber 5 to control the flow of vapor therefrom, as will appear. The inlet end 45 of the hollow mandrel 15 is connected by suitable means with a supply of vapor for chemical vapor deposition. This vapor is forced through the mandrel 15 and escapes into the welded tube 23 through the openings 31. Because the mandrel head 33 acts substantially as a plug in the die 27, the vapor which escapes from the openings 31 flushes back through the welded tube 23, through the heated region 38, escaping through the curling die 17 into the chamber 5. The annular space between the mandrel 15 and the tube 23 is enough to accommodate a substantial flow through the welded tube 23. The vapor flow is shown by the darts in the drawings. The control at the outlet 43 determines the rate at which the vapor flows.

Operation is as follows:

A strip 11 of the proper dimensions and composition for the tubing desired is fed through the chamber 5 and formed into tubular shape by-the die 17, welding occurring at the location of the Welder 21. The resulting welded tube 23 in the second chamber 7 has its outside exposed to whatever gas is carried in chamber 7. This gas may form a neutral atmosphere, such as, for example, argon, or it may be an oxide-reducing gas if it is desired to remove any oxide that may be on the outside of the tube 23, if metallic. In the latter case the gas may be hydrogen, cracked ammonia or the like. The use of such atmospheres may be omitted under some circumstances.

The vapor which is fed through the mandrel 15 and which flushes back around it within the welded tube 23 passes through the heating zone 38 effected by the heating coils 37. The temperature established in this zone by the coils 37 is that which will decompose this vapor into the material which is to be vapor-deposited on the inside of the tubing and the gaseous decomposition products. Undeposited gaseous decomposition products are forced back through the tube 23, out of the die 17 and into the chamber 5, from which they escape through the controlled outlet 43. The decomposition product or material deposited on the inside of tube 23 covers its linear weld as well as its other inside portions. The unused vapor which is flushed back and out of the chamber 5 through outlet 43 may be purified and recycled, as desired.

If it is desired to apply a coating on the outside of the tube 23, as well as on its inside, then an atmosphere is carried in chamber 7 which is of the proper composition for chemical vapor decomposition in the heating zone of the coils 37. This will form a deposit on the outside of the tube. If it is to form the same coating as on the inside of the tube, then the same type of vapor is provided in the chamber 7 as enters through the hollow mandrel 15. If a different exterior coating is desired, then another appropriate vapor for chemical vapor deposit will be carried in chamber 7.

Examples of vapors that may be used for chemical vapor deposition at appropriate temperatures on the substrate materials of which the welded tube 23 may be composed are as follows, the transforming equations being given, said equations showing the reaction temperature to be maintained in region 38 for deposition:

2Al(C H 360 C. 2Al+3H2+6C4Hg to deposit aluminum on steel or copper tube.

2CbCl +5H 1250 C. 2Cb+l0HCl to deposit columbium on a variety of metals for the tube.

WF +3H 500 to 750 C. W+6HF to deposit tungstem on a copper or nickel tube.

l2H O to deposit tungsten carbide on a steel tube.

B N H Cl 1300" c. 3BN+3HC1 to deposit boron nitride on a molybdenum or tantalum tube.

The above examples are not to be taken as limiting, inasmuch as there are many other known chemical vapor transformations that occur and which maybe used in connection with an appropriate substrate (tube 23). It will be understood that the principles of the invention are applicable to the use of nonmetals for the tubing and lining.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

What is claimed is:

1. Apparatus for manufacturing a lined tube, comprising means for moving a tube, a drawing die through which the tube is drawn, a hollow mandrel extending into the tube, said mandrel having a plug disposed at the end thereof which is adapted to cooperate with said die and an outlet means located in front of said plug for introducing into the tube and flushing therethrough oppositely to the movement of the tube a vapor which is decomposable to form a vapor deposit at an elevated temperature, and means for heating the tube to the decomposition temperature in the flushed region thereof, whereby deposition of lining material occurs on the inside of the tube.

2. Apparatus for manufacturing a lined tube, comprising a curling means, means for drawing a strip through the curling means to curl the strip into a moving form having adjacent margins, means for continuously bonding the adjacent margins to form a seamed moving tube, a hollow mandrel extending into the second tube from the curling means and beyond the bonding means, said mandrel supporting a plug in the seamed tube as the tube moves and having outlet means between the plug and the bonding means to introduce into and flush through a part of the tube a vapor which is decomposable to form a vapor deposit at an elevated temperature, and means for heating the tube to the decomposition temperature between the point of bonding and the point of vapor introduction, whereby deposition of lining material occurs on the inside of the tube as the vapor flushes through it. I

3. Apparatus for manufacturing a lined metal tube, comprising a curling die, means for drawing a metal strip through the die to curl the strip into a moving metallic tubular form having adjacent margins, means for continuously welding the margins as they are brought together by the die to form a seamed moving tube, a hollow mandrel extending into the seamed tube through the die and beyond the welding means, said mandrel supporting a plug in the seamed tube as the tube moves and having outlet means between the plug and the welding means to introduce into the tube a vapor which is decomposable to form a vapor deposit at an elevated temperature, and means for heating the tube to the decomposition temperature between the point of welding and the point of vapor introduction, whereby deposition of lining material occurs on the inside of the tube.

4. Apparatus for manufacturing a metal-lined seamed tube, comprising a curling die, means for drawing a metal strip through the die to curl the strip into a moving tubular form having adjacent margins, means for continuously welding the margins as they are brought together by the die to -form a moving seam-welded metal tube, a hollow mandrel extending through the die into the welded tube and beyond the welding means, said mandrel supporting a plug in the second tube at its moves and having outlet means between the plug and the welding means to introduce into the tube a vapor which is decomposable to form a metallic vapor deposition at an elevated temperature, means for heating the tube to the decomposition temperature between the point of welding and the point of vapor introduction, whereby deposition of metal occurs on the inside of the tube, including its welded seam, and means for passing a like vapor over the outside of the tube at said point continuously to deposit metal on the outside of the tube.

References Cited UNITED STATES PATENTS 2,982,312 5/1961 Caplan et a1. 29429 X 3,007,810 11/1961 Hobrock ll7-97 X 3,031,338 4/1962 Bourdeau 117-97 MORRIS KAPLAN, Primary Examiner US. Cl. X.R. 72-46; 1l849.5 

